Image display device, portable terminal device, display panel and image display method using the same

ABSTRACT

A three-dimensional image/two-dimensional image display device includes a plurality of display pixels, and a lenticular lens for three-dimensional display. Each display pixel is consisted of M×N number of sub-pixels to be viewed from N view points. A pitch a of sub-pixels arranged in the longitudinal direction of ridge projection of the lenticular lens and a pitch b of the sub-pixels arranged in a direction orthogonal to the longitudinal direction of the lenticular lens satisfy the following expression. The M×N number of sub-pixels included in each of said display pixels are formed within a square area.
 
a:b=N:1

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to an image display device which iscapable of individually displaying images that are to be viewed from aplurality of view points and displaying an image without reducingresolution when images different from one another are viewed from theplurality of view points, a portable terminal device incorporatingtherein such image display device, a display panel incorporated withinthe image display device, and an image display method. Particularly, thepresent invention relates to an image display device capable ofdisplaying a three-dimensional image without reducing resolution,displaying a two-dimensional image and three-dimensional image with thesame resolution, and further, displaying a two-dimensional image andthree-dimensional image at any location in a blended fashion, a portableterminal device incorporating therein such image display device, adisplay panel incorporated within the image display device, and an imagedisplay method using the same.

2. Description of the Related Art

Conventionally, a display device has been studied which is capable ofdisplaying a three-dimensional image. In 280 years B.C.,Greece-mathematician Euclid considered and defined “binocular vision iswhat a person perceives when he/she sees, using his/her right and lefteyes one at a time, different images of the same object that are createdwhen viewed from different directions” (non-patent literature 1: ChihiroMasuda, “Three-Dimensional Display” Sangyo Tosho, K.K.). That is, athree-dimensional display device should have a capability to distributeimages with parallax to right and left eyes, respectively.

A number of three-dimensional image display methods have conventionallybeen studied and developed as a method for realizing the above-statedcapability and those methods can be classified mainly into two types ofmethods, i.e., a method using eyeglasses and a method not usingeyeglasses. One of methods of the type using eyeglasses would be ananaglyph method using difference in color, a polarized eyeglasses methodusing polarization, or the like. However, in the method usingeyeglasses, a user of eyeglasses basically cannot remove the burden ofwearing eyeglasses and in consideration of such problems, non-eyeglassesobserving, which is performed by not using eyeglasses, has intenselybeen studied and developed in recent years. The non-eyeglasses observingincludes, for example, a method using a lenticular lens and a methodusing a parallax barrier.

The parallax barrier method was conceived by Berthier in 1896 andidentified by Ives as practical in 1903. FIG. 1 shows an optical modelillustrating a three-dimensional image display method using a parallaxbarrier. As shown in FIG. 1, a parallax barrier 105 is a barrier (lightshield) which has a number of fine vertical-striped openings, i.e.,slits 105 a formed therein. Furthermore, disposed in the vicinity of onesurface of the parallax barrier 105 is a display panel 106. In thedisplay panel 106, pixels 123 for right eye and pixels 124 for left eyeare arranged in a direction orthogonal to the longitudinal direction ofthe slits. Moreover, disposed in the vicinity of the other surface ofthe parallax barrier 105, i.e., on the side opposite the display panel106 is a light source 108.

Lights were emitted from the light source 108 and have transmittedthrough the openings (slits 105 a) of the parallax barrier 105 and thenthrough the pixels 123 for right eye, thereby flowing out as lightfluxes 181. Similarly, lights were emitted from the light source 108 andhave transmitted through the slits 105 a and then through the pixels 124for left eye, thereby flowing out as light fluxes 182. In this case, thelocation of an observer who is able to identify a three-dimensionalimage is determined by a positional relationship between the parallaxbarrier 105 and the pixels. That is, it is required that a right eye 141of the observer 104 falls within an area through which all of the lightfluxes 181 corresponding to a plurality of pixels 123 for right eye passand a left eye 142 of the observer 104 falls within an area throughwhich all of the light fluxes 182 corresponding to a plurality of pixels124 for left eye pass. As shown in FIG. 1, this positional relationshipbetween the eyes and the light fluxes corresponds to the case where amidpoint 143 between the right eye 141 and left eye 142 of the observerfalls within a quadrangle shaped three-dimensional visible range 107shown in FIG. 1. Among line segments extending in a direction alongwhich the pixels 123 for right eye and pixels 124 for left eye arearranged in the three-dimensional visible range 107, a line segmentpassing through a intersection 107 a of diagonal lines in thethree-dimensional visible range 107 is longest. Accordingly, in case ofthe midpoint 143 being positioned at the intersection 107 a, a latitudeof a displacement which is allowed when the position of the observer isdisplaced in a right or left direction becomes maximum and therefore,when the midpoint 143 is positioned at the intersection 107 a, it can beconcluded that the observer views images from a most preferableposition. In consideration of the above-described fact, it isrecommended that the three-dimensional image display method isconstructed such that when assuming a distance between the intersection107 a and the display panel 106 is an optimal observation distance OD,the observer views images keeping the distance OD from the displaypanel. Note that a virtual plane spaced apart from the display panel 106the optimal observation distance OD in the three-dimensional visiblerange 107 is referred to as an optimal observation plane 107 b. Thisallows lights from the pixels 123 for right eye and the pixels 124 forleft eye to reach the right eye 141 and left eye 142 of the observer,respectively. Therefore, it becomes possible that the observeridentifies an image displayed on the display panel 106 as athree-dimensional image.

At the beginning of emergence of the method using a parallax barrier,the parallax barrier was disposed between pixels and eyes, andtherefore, a problem arises in that the parallax barrier obstructs theview and serves to cause the visibility of an image to be displayed tobe low. However, the recent commercialization of a liquid crystaldisplay panel makes it possible to dispose the parallax barrier 105 onthe rear side of the display panel 106 to improve the visibility of animage to be displayed. This currently leads to enhancement of the studyand development of a three-dimensional image display device using aparallax barrier.

An example of a product which uses a parallax barrier and became acommercial reality is described in a table 1 of Nikkei Electronics, No.838, pp. 26-27 issued on Jan. 6, 2003 (non-patent literature 2). Thisproduct is a cellular phone incorporating therein a 3D(three-dimensional) liquid crystal display panel and the liquid crystaldisplay panel making up a three-dimensional image display device is2.2-inch diagonal in size and has 176 columns of 220 dots as a displaydot. Furthermore, a liquid crystal display panel for switching betweenon and off of effect of parallax barrier is provided allowing a displayon the panel to switch between three-dimensional display andtwo-dimensional display. Although the display device displays atwo-dimensional image with a definition of 128 dpi in both vertical andhorizontal directions, at the time of display of three-dimensionalimage, the display device displays images for left eye and images forright eye in a vertical stripe form and in an alternate fashion, andtherefore, the display device displays the image with a definition of 64dpi in a horizontal direction, which definition is half the definition,128 dpi, in a vertical direction.

Furthermore, the method using a lenticular lens is invented by Ives etal. in around 1910, as described in, for example, the aforementionednon-patent literature 1. FIG. 2 is a perspective view illustrating alenticular lens and FIG. 3 shows an optical model illustrating athree-dimensional display method using a lenticular lens. As shown inFIG. 2, a lenticular lens 121 is constructed such that one surface ofthe lens is planarized to provide a plane and the other surface thereofhas formed therein a plurality of hog-backed projections (cylindricallens 122), each extending in one direction, so that the longitudinaldirections of the projections are parallel to one another.

Moreover, as shown in FIG. 3, a three-dimensional image display deviceof the type using a lenticular lens is configured so that a lenticularlens 121, a display panel 106 and a light source 108 are arranged inthis order when viewed by an observer, and pixels of the display panel106 are positioned on a focal plane of the lenticular lens 121. Thedisplay panel 106 is constructed such that pixels 123 for display of animage for right eye 141 and pixels 124 for display of an image for lefteye 142 are arranged in an alternate fashion. In this case, individualsets of the pixel 123 and pixel 124, those pixels being adjacent eachother, are provided so as to correspond to the cylindrical lenses(projections) 122 of the lenticular lens 121, respectively. This allowslight emitted from the light source 108 and having transmitted throughthe individual pixels to be distributed by the cylindrical lenses 122 ofthe lenticular lens 121 in directions toward left and right eyes. Thus,it becomes possible for the left and right eyes to identify imagesdifferent from each other, thereby allowing an observer to identify athree-dimensional image.

Whereas the method using a parallax barrier is the method for“shielding” unnecessary light rays by using a barrier, the method usinga lenticular lens is the method for changing a direction in which lightpropagates and therefore it can be concluded that providing thelenticular lens theoretically never reduces the brightness of displayscreen. Accordingly, application of the method using a lenticular lensto a portable device etc. whose ability to display images with highbrightness and operate with low power is regarded as particularlyimportant is promising.

An example of a three-dimensional image display device developed using alenticular lens is described in the above-stated non-patent literature2. A liquid crystal display panel making up a three-dimensional imagedisplay device is 7-inch diagonal in size and has 800 columns of 480dots as a display dot. Furthermore, changing a distance between alenticular lens and a liquid crystal display panel by 0.6 mm allowsswitching between three-dimensional display and two-dimensional display.The number of view points arranged in a horizontal direction is five andwhen an observer changes his/her viewing angle in a horizontaldirection, he/she can view five different images. That is, a displaydefinition achieved at the time of display of three-dimensional image isreduced to one fifth of a display definition achieved at the time ofdisplay of two-dimensional image.

Furthermore, a simultaneous multiple-image display for simultaneouslydisplaying multiple images has been developed as an image display deviceusing a lenticular lens (for example, refer to the patent literature 1:Japanese Patent Laid-Open Publication No. H06(1994)-332354 (FIG. 13)).This display is configured so that through use of lenticular lensability to distribute images, images different from one another whenviewed from different directions are simultaneously displayed under thesame conditions. This allows a single simultaneous multiple-imagedisplay to simultaneously provide a plurality of observers, who arepositioned in directions different from one another relative to thedisplay, with images different from one another. The patent literature 1discloses that when using the simultaneous multiple-image display,saving of space for arrangement of displays and reduction in electricityexpense are achieved, but those beneficial effects cannot be obtained inthe case where a number of displays corresponding to the number ofobservers are prepared.

However, the aforementioned conventional techniques have the followingproblems. That is, when displaying images different from one another sothat the images are viewed from a plurality of view points, theresolution of individual images to be displayed is disadvantageouslyreduced. Particularly, the resolution of an image to be displayed isreduced to a greater extent at the time of display of three-dimensionalimage than at the time of display of two-dimensional image. FIG. 4 is atop view illustrating sub-pixels in the aforementioned three-dimensionalimage display device using the parallax barrier and allowing view fromtwo view points. One display pixel to be used at the time of display ofthree-dimensional image is comprised of two display pixels to be used atthe time of display of two-dimensional image. At the time of display ofthree-dimensional image, the two display pixels serve as a pixel forleft eye and a pixel for right eye to allow the display device todisplay an image for left eye and an image for right eye, respectively.The pixel for left eye and the pixel for right eye each are comprised ofthree primary color sub-pixels with primary colors, red, blue and green,and three slit openings correspond to one display pixel. In more detail,the red sub-pixel 411 for left eye and the green sub-pixel 422 for righteye correspond to a first slit opening. Furthermore, the blue sub-pixel413 for left eye and the red sub-pixel 421 for right eye correspond to asecond slit opening. Still furthermore, the green sub-pixel 412 for lefteye and the blue sub-pixel 423 for right eye correspond to a third slitopening. Note that the individual sub-pixels are partitioned by a lightshield section 6. When assuming a pitch of primary color sub-pixelsarranged in the longitudinal direction (vertical direction 11) of slitopening is a and a pitch of the primary color sub-pixels arranged in adirection (horizontal direction 12) orthogonal to the longitudinaldirection of slit opening is b, the following expression 1 results.a:b=3:1  (Expression 1)

As a result, a relationship between a pitch a of display pixels arrangedin the longitudinal direction of slit opening and a pitch c of thedisplay pixels arranged in a direction orthogonal to the longitudinaldirection of slit opening is represented by the following expression 2.That is, when a three-dimensional image is displayed by thethree-dimensional image display device shown in FIG. 4, the size of onedisplay pixel is represented by a in the longitudinal direction of slitopening and by c in the direction orthogonal to the longitudinaldirection.a:c=1:2  (Expression 2)

On the other hand, when a two-dimensional image is displayed by thethree-dimensional image display device shown in FIG. 4, the parallaxbarrier 105 is removed and the one display pixel to be used at the timeof display of three-dimensional image is used as two display pixels.Note that a method for removing a parallax barrier includes, forexample, constructing a parallax barrier by a liquid crystal displaypanel for switching between on and off of effect of parallax barrier, asshown in the aforementioned non-patent literature 2, and changing lighttransmittance of individual elements of the liquid crystal displaypanel. Furthermore, when a lenticular lens is used instead of parallaxbarrier, changing a distance between the display panel and thelenticular lens allows elimination of effects of the lenticular lens.

In more detail, at the time of display of two-dimensional image, asshown in FIG. 4, three sub-pixels, i.e., the red sub-pixel 411 for lefteye, green sub-pixel 422 for right eye and blue sub-pixel 413 for lefteye, are used as one display pixel and three sub-pixels, i.e., the redsub-pixel 421 for right eye, green sub-pixel 412 for left eye and bluesub-pixel 423 for right eye, are used as one display pixel. As a result,the size of one display pixel is represented by a in the longitudinaldirection of slit opening and by (c/2) in the direction orthogonal tothe longitudinal direction. Therefore, it turns out that the pitch, usedat the time of display of three-dimensional image, of the pixelsarranged in the direction orthogonal to the longitudinal direction ofslit opening becomes twice the pitch, used at the time of display oftwo-dimensional image, of the pixels arranged in the same direction.Accordingly, as is the case with the three-dimensional image displaydevice described in the aforementioned non-patent literature 1, theresolution of an image to be displayed at the time of display ofthree-dimensional image in the horizontal direction 12 is reduced tohalf the resolution of an image to be displayed at the time of displayof two-dimensional image.

The reduction in the resolution of an image to be displayed becomesproblematic particularly when a three-dimensional image is displayedtogether with character information and when character information isthree-dimensionally displayed. Since the display pixel is caused to takea shape of a rectangle with a 1:2 aspect ratio, the resolution in ahorizontal direction is reduced and lack is generated in a vertical linemaking up a character when the character is displayed. As a result, thevisibility of a character to be displayed is reduced to a large extent.This problem becomes more prominent as the number of view pointsincreases.

Problems similar to those described above are not limited to athree-dimensional image display device, but generally observed in thedisplay device for displaying images so that the images are viewed froma plurality of view points. That is, when displaying images so that theimages are viewed from a plurality of view points different from oneanother; the resolution of images arranged in a direction in whichsub-pixels that are to be viewed from a plurality of view points arearranged is reduced to an extent larger than the resolution achieved atthe time of display of a single image and especially when a character isdisplayed together with the images to be viewed from a plurality of viewpoints, the visibility of character is disadvantageously andsignificantly reduced.

Furthermore, a problem arises in that when using the conventionaltechniques relating to the aforementioned three-dimensional imagedisplay device, switching between three-dimensional display andtwo-dimensional display is performed all over the screen and thereforeit is impossible that a three-dimensional image and a two-dimensionalimage are displayed on any location in a blended fashion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an image displaydevice which is capable of displaying an image without reducingresolution when images different from one another are viewed from aplurality of view points, particularly when a three-dimensional image isdisplayed, displaying a character with high visibility, displaying atwo-dimensional image and three-dimensional image with the sameresolution, and displaying a three-dimensional image and two-dimensionalimage at any position in a blended fashion, a portable terminal deviceincorporating therein such image display device, a display panelincorporated within the image display device, and an image displaymethod using the same.

An image display device according to the first aspect of the presentinvention comprises: a display panel which is to be viewed from N numberof view points and includes a plurality of display pixels arranged in amatrix, each display pixel having M×N (M and N each represent a naturalnumber) number of sub-pixels, said M×N number of sub-pixels included ineach of said display pixels being formed within a square area; and alenticular lens for distributing light rays from said sub-pixelsindividually to said view points.

In the invention, the M×N number of sub-pixels included in one of theplurality of display pixels are formed within a square area. Therefore,the display pixel allows images to be independently viewed from the Nview points. Furthermore, if N is not less than 2, an image for righteye and an image for left eye can be distributed to view pointsdifferent from each other, allowing display of three-dimensional image.In this case, the display pixel is caused to take a shape of square.Additionally, when the same image is displayed by the N number ofsub-pixels, in other words, the N number of sub-pixels making up onedisplay pixel are operated to emit lights with the same intensity, theimage display device, comprising such N number of sub-pixels, in itsentirety is able to display a two-dimensional image. In this case, theresolution of the image is the same as that achieved when athree-dimensional image is displayed and the display pixel is caused totake a shape of square. In this way, in the invention, since resolutionsachieved at the time of display of three-dimensional image and at thetime of display of two-dimensional image can be made equal to eachother, displaying a three-dimensional image and two-dimensional image ina blended fashion never causes an observer to feel uncomfortable,allowing a three-dimensional image to be displayed in any place where atwo-dimensional image is to be displayed. Furthermore, since the displaypixel can be caused to take a shape of square, an image is displayedwith high visibility and particularly, a character is displayed withhigh visibility. Likewise, also when two-dimensional images differentfrom one another are displayed as images viewed from N view points, thedisplay pixel can be caused to take a shape of square, preventingreduction in the resolution of each of the two-dimensional images andimproving especially the visibility of a character to be displayed.

Furthermore, the above-described display panel is a monochrome displaypanel and M represents 1, and when assuming a pitch of sub-pixelsarranged in a longitudinal direction along a ridge projection of thelenticular lens is a and a pitch of the sub-pixels arranged in adirection orthogonal to the longitudinal direction of the lenticularlens is b, those pitches may satisfy the following expression 3,a:b=N:1  (Expression 3)

Alternatively, the display panel is a color display panel comprisingsub-pixels of three primary colors and M represents 3, and when assuminga pitch of the sub-pixels arranged in a longitudinal direction along aridge projection of the lenticular lens is a and a pitch of thesub-pixels arranged in a direction orthogonal to the longitudinaldirection of the lenticular lens is b, those pitches may satisfy thefollowing expression 4.a:b=3×N:1  (Expression 4)

As described above, since each of the display pixels has sub-pixels ofthree primary colors, a color display can be made.

Alternatively, the display panel is a color display panel comprisingsub-pixels of three primary colors and M represents 3, and wherein whenassuming a pitch of the sub-pixels arranged in a longitudinal directionalong a ridge projection of the lenticular lens is a and a pitch of thesub-pixels arranged in a direction orthogonal to the longitudinaldirection of a ridge projection of the lenticular lens is b, thosepitches may satisfy the following expression 5.a:b=N:3  (Expression 5)

Accordingly, three sub-pixels are arranged in the longitudinal directionof the lenticular lens and N number of sub-pixels are arranged in adirection orthogonal to the longitudinal direction, meaning that thesub-pixels can be arranged in a distributed fashion in vertical andhorizontal directions of the display device. As a result, the density ofpixels in the horizontal direction of the display device is reduced,advantageously allowing the display device to easily be manufactured.

An image display device according to the second aspect of the presentinvention comprises: a display panel which is to be viewed from N numberof view points and includes a plurality of display pixels, eachincluding N (N represents a natural number) number of sub-pixels; and alenticular lens. Said image display device is further constructed suchthat when assuming a pitch of a lens array in said lenticular lens is L,a pitch of said sub-pixels of said display pixel is P, a pitch of saidsub-pixels arranged in a longitudinal direction along a ridge projectionof said lenticular lens is a, and a pitch of said sub-pixels arranged ina direction orthogonal to said longitudinal direction of said lenticularlens is b, said pitches satisfy the following expression 6.a:b=L:P  (Expression 6)

In the invention, since the display pixel has the shape defined by theabove-described expression 6, the display pixel appears as a precisesquare when viewed through the lenticular lens. Furthermore, if N is notless than 2, an image for right eye and an image for left eye can bedistributed to view points different from each other, allowing displayof three-dimensional image. Moreover, when the same image is displayedby the N number of sub-pixels, in other words, the N number ofsub-pixels making up one display pixel are operated to emit lights withthe same intensity, a two-dimensional image can be displayed as a wholeby the image display device. In this way, since resolutions achieved atthe time of display of three-dimensional image and at the time oftwo-dimensional image can be made equal to each other, displaying athree-dimensional image and two-dimensional image in a blended fashionnever causes an observer to feel uncomfortable, allowing athree-dimensional image to be displayed in any place where atwo-dimensional image is to be displayed. Furthermore, since the displaypixel is allowed to appear as a precise square, an image is displayedwith high visibility and particularly, a character is displayed withhigh visibility. Likewise, also when two-dimensional images differentfrom one another are displayed as images to be viewed from N viewpoints, the display pixel can be caused to take a shape of square,preventing reduction in the resolution of each of the two-dimensionalimages and improving especially the visibility of a character to bedisplayed.

An image display device according to the third aspect of the presentinvention comprises: a display panel which is to be viewed from N numberof view points and includes a plurality of display pixels, eachincluding 3×N (N represents a natural number) number of primary colorsub-pixels; and a lenticular lens. Said image display device is furtherconstructed such that when assuming a pitch of a lens array in saidlenticular lens is L, a pitch of said sub-pixels of said display pixelis P, a pitch of said sub-pixels arranged in a longitudinal directionalong a ridge projection of said lenticular lens is a, and a pitch ofsaid sub-pixels arranged in a direction orthogonal to said longitudinaldirection of said lenticular lens is b, said pitches satisfy thefollowing expression 7.a:b=3×L:P  (Expression 7)In the invention, the display pixel is allowed to appear as a precisesquare and further a color image can be displayed.

An image display device according to the fourth aspect of the presentinvention comprises: a display panel which is to be viewed from N numberof view points and includes a plurality of display pixels, eachincluding 3×N (N represents a natural number) number of primary colorsub-pixels; and a lenticular lens. Said image display device is furtherconstructed such that when assuming a pitch of a lens array in saidlenticular lens is L, a pitch of said sub-pixels of said display pixelis P, a pitch of sub-pixels arranged in a longitudinal direction along aridge projection of said lenticular lens is a, and a pitch of saidsub-pixels arranged in a direction orthogonal to said longitudinaldirection of said lenticular lens is b, said pitches satisfy thefollowing expression 8.a:b=L/3:P  (Expression 8)

In the invention, since the pitch of the sub-pixels arranged in thelongitudinal direction of the lenticular lens is L, the display pixelcan be caused to take a shape of perfect square. Furthermore, a colorimage can be displayed. Moreover, three display pixels are arranged inthe longitudinal direction of the lenticular lens and N number ofdisplay pixels are arranged in a direction orthogonal to thelongitudinal direction, meaning that the display pixels can be arrangedin a distributed fashion in vertical and horizontal directions of thedisplay device. As a result, the density of pixels in the horizontaldirection of the display device is reduced, advantageously allowing thedisplay device to easily be manufactured.

Additionally, the above-described primary color sub-pixels having thesame color may be arranged in a direction orthogonal to the longitudinaldirection of the lenticular lens.

Alternatively, in the image display device according to the invention, aset of three sub-pixels having the same relative positional relationshipto a central axis of the lenticular lens and positioned adjacent oneanother may constitute primary color sub-pixels with primary colors,red, blue and green.

In the invention, the primary color sub-pixels are arranged not in astripe pattern but in a mosaic pattern, allowing the display device tobe suited to display an image of natural scene, etc.

Furthermore, in the image display device according to the invention, afocal distance of the lenticular lens and a distance between an apex ofthe lens and the pixel may be different from each other. This causeslight emitted from the lenticular lens to reach an observer in a spreadfashion. As a result, the degree to which the display device isinfluenced by a light shield section can be reduced. This prevents viewof two-dimensional image from an area in which illuminance is reduced,allowing the resulting quality of a two-dimensional image to bedisplayed to be increased.

Still furthermore, the longitudinal direction along the ridge projectionof the lenticular lens may be a horizontal direction of an image to bedisplayed. This means that when the image display device is incorporatedwithin a portable terminal device, only changing the angle of theportable terminal device allows an observer to view the image displaydevice from a plurality of view points different from one another,enabling the observer to view a plurality of images. Particularly, whenthe plurality of images are associated with one another, the observer isable to view the individual images simply by changing a viewing angleand therefore the portable terminal device becomes highly convenient forthe observer. Moreover, since the plurality of view points are arrangedin the vertical direction of the images, the observer is able to viewthe individual images through his/her both eyes without fail, allowingthe visibility of the individual images to be enhanced

An image display device according to the fifth aspect of the presentinvention comprises: a display panel which is to be viewed from N numberof view points and includes a plurality of display pixels arranged in amatrix, each display pixel having M×N (M and N each represent a naturalnumber) number of sub-pixels, said M×N number of sub-pixels included ineach of said display pixels being formed within a square area; and aparallax barrier for distributing light rays from said sub-pixelsindividually to said view points.

In the invention, although the use of lenticular lens causes reductionin the quality of an image to be displayed, the use of parallax barrierprevents occurrence of reduction in the quality of an image to bedisplayed, which reduction is due to a pattern in the lens.

Moreover, the longitudinal direction of a slit opening in the parallaxbarrier may be a horizontal direction of an image to be displayed. Thismeans that when the image display device is incorporated within aportable terminal device, only changing the angle of the portableterminal device allows an observer to view a plurality of images from aplurality of view points different from one another.

The portable terminal device according to the invention may be acellular phone, portable terminal, PDA, game machine, digital camera ordigital video camera.

A display panel according to the sixth aspect of the present inventioncomprises a plurality of display pixels arranged in a matrix, eachdisplay pixel being to be viewed from N view points and including N (Nrepresents a natural number) number of sub-pixels, wherein said displaypanel is a monochrome display panel and when assuming a pitch of saidsub-pixels arranged in one direction is a and a pitch of said sub-pixelsarranged in a direction orthogonal to said one direction is b, anexpression a:b=N:1 results.

A color display panel according to the seventh aspect of the presentinvention comprises a plurality of display pixels arranged in a matrix,each display pixel being to be viewed from N view points and including3×N (N represents a natural number) number of three primary colorsub-pixels. Said display panel is further constructed such that whenassuming a pitch of said sub-pixels arranged in one direction is a and apitch of said sub-pixels arranged in a direction orthogonal to said onedirection is b, an expression a:b=3×N:1 results.

A color display panel according to the eighth aspect of the presentinvention comprises a plurality of display pixels arranged in a matrix,each display pixel being to be viewed from N view points and including3×N (N represents a natural number) number of three primary colorsub-pixels, said display panel being further constructed such that whenassuming a pitch of said sub-pixels arranged in one direction is a and apitch of said sub-pixels arranged in a direction orthogonal to said onedirection is b, an expression a:b=N:3 results.

The above-described display panel can be incorporated within an imagedisplay device and when the one direction is made parallel to thelongitudinal direction of the ridge projection of the lenticular lens ofa three-dimensional image/two-dimensional image display device or thelongitudinal direction of the slit opening of the parallax barrier, thedisplay panel can be caused to take a shape of square and the visibilityof an image to be displayed can be improved.

An image display method according to the ninth aspect of the presentinvention is characterized in that, at the time of display ofthree-dimensional image, at least M×2 number of sub-pixels for two viewpoints of left-eye and right eye in M×N (M represents a natural numberand N represents a natural number not less than 2) number of sub-pixelsfor N view points included in each of a plurality of display pixelsarranged in a matrix to constitute a display panel, display images withparallax and a lenticular lens distributes light rays emitted from saidsub-pixels for two view points individually to said view points; and atthe time of display of two-dimensional image, said sub-pixels for twoview points of left eye and right eye display images without parallax,said M×N number of sub-pixels included in each of said display pixelsbeing formed within a square area.

An image display method according to the tenth aspect of the presentinvention is characterized in that, at the time of display ofthree-dimensional image, at least N×2 number of sub-pixels for two viewpoints of left-eye and right eye in M×N (M represents a natural numberand N represents a natural number not less than 2) number of sub-pixelsfor N view points included in each of a plurality of display pixelsarranged in a matrix to constitute a display panel, display images withparallax and a parallax barrier distributes light rays emitted from saidsub-pixels for two view points individually to said view points; and atthe time of display of two-dimensional image, said sub-pixels for twoview points of left eye and right eye display images without parallax,said M×N number of sub-pixels included in each of said display pixelsbeing formed within a square area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical model diagram illustrating a three-dimensionalimage display method using a parallax barrier;

FIG. 2 is a perspective view illustrating a lenticular lens;

FIG. 3 shows an optical model illustrating a three-dimensional displaymethod using a lenticular lens;

FIG. 4 is a top view illustrating sub-pixels in the conventionalthree-dimensional image display device;

FIG. 5 is a perspective view illustrating an image display deviceaccording to a first embodiment of the invention;

FIG. 6 is a perspective view illustrating a portable terminal deviceaccording to the embodiment;

FIG. 7 is a top view illustrating sub-pixels of the image display deviceaccording to the embodiment;

FIG. 8 shows an optical model illustrating how the image display deviceaccording to the embodiment operates;

FIG. 9 shows an optical model illustrating a dual eye typethree-dimensional image display device using a typical lenticular lens;

FIG. 10 shows an optical model illustrating how the simulation isperformed in the embodiment;

FIG. 11 is a graph resulting from the simulation, in which axis ofabscissas denotes the coordinate of a observing position on the lightreception surface and axis of ordinate denotes illuminance at theobserving position;

FIG. 12 is a graph resulting from the simulation, in which axis ofabscissas denotes the coordinate of a observing position on the lightreception surface, axis of ordinate denotes an illuminance at theobserving position, and the focal distance of lenticular lens is assumedto be 1.88 mm;

FIG. 13 is a perspective view illustrating an image display deviceaccording to a second embodiment of the invention;

FIG. 14 is a top view illustrating a pitch of sub-pixel arranged in thedisplay device;

FIG. 15 is a perspective view illustrating an image display deviceaccording to a third embodiment of the invention;

FIG. 16 is a top view illustrating a pitch of sub-pixels arranged in thedisplay device;

FIG. 17 is a perspective view illustrating an image display deviceaccording to a fourth embodiment of the invention;

FIG. 18 is a top view illustrating a pitch of sub-pixels arranged in thedisplay device;

FIG. 19 is a perspective view illustrating an image display deviceaccording to a fifth embodiment of the invention;

FIG. 20 is a top view illustrating a pitch of sub-pixels arranged in thedisplay device;

FIG. 21 is a perspective view illustrating an image display deviceaccording to a sixth embodiment of the invention;

FIG. 22 is a top view illustrating a pitch of sub-pixels arranged in thedisplay device;

FIG. 23 is a perspective view illustrating an image display deviceaccording to a seventh embodiment of the invention;

FIG. 24 is a top view illustrating a pitch of sub-pixels arranged in thedisplay device;

FIG. 25 is a perspective view illustrating an image display deviceaccording to an eighth embodiment of the invention;

FIG. 26 is a perspective view illustrating a portable terminal deviceaccording to a ninth embodiment of the invention;

FIG. 27 shows an optical model illustrating how the image display deviceaccording to the embodiment operates.

THE PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the invention will be explained in detail belowwith reference to the attached drawings.

First Embodiment

FIG. 5 is a perspective view illustrating an image display deviceaccording to a first embodiment of the invention and FIG. 6 is aperspective view illustrating a portable terminal device according tothe embodiment, and FIG. 7 is a top view illustrating sub-pixels of theimage display device according to the embodiment. The image displaydevice according to the embodiment is a three-dimensionalimage/two-dimensional image display device capable of displaying imagesso that the images are independently viewed from two viewing points,i.e., a view point for left eye and a view point for right eye, anddisplaying both the three-dimensional image and the two-dimensionalimage. As shown in FIG. 5, the three-dimensional image/two-dimensionalimage display device 1 (hereinafter; also referred to simply as athree-dimensional display device 1) according to the embodiment hasprovided therein a lenticular lens 3, a display panel 2 and a lightsource (not shown) in this order when those components are viewed fromthe location of an observer. The display panel 2 would be, for example,a transmissive liquid crystal display panel. The display panel 2 iscomprised of a number of display pixels and in this case, one displaypixel consists of two sub-pixels 41 and 42.

Furthermore, the lenticular lens 3 has a plurality of cylindrical lenses3 a arranged in parallel to one another. In the embodiment, thelongitudinal direction of the cylindrical lens 3 a is assumed to be avertical direction 11 and the direction along which the cylindricallenses 3 a are arranged is assumed to be a horizontal direction 12. Onecylindrical lens 3 a out of the plurality of cylindrical lenses thatmake up the lenticular lens 3 is disposed so as to correspond to theindividual sub-pixels 41, 42 of the display panel 2 and the individualsub-pixels 41, 42 serve respectively as a sub-pixel 41 for left eye anda sub-pixel 42 for right eye, based on their positional relationshipwith respect to the cylindrical lens 3 a. Provided between theindividual sub-pixels is a light shield section 6. The light shieldsection 6 is disposed for the purpose of preventing mixture of colors ofimages and sending a display signal to a pixel.

How a pitch of the sub-pixels arranged is designed in the case where thesub-pixel 41 for left eye and the sub-pixel 42 for right eye are notdiscriminated from each other is shown in FIG. 7. That is, a ratio of apitch a of the sub-pixels arranged in the longitudinal direction(vertical direction 11) of the lenticular lens 3 to a pitch b of thesub-pixels arranged in the direction (horizontal direction 12)orthogonal to the longitudinal direction of the lenticular lens 3 is2:1.

Furthermore, as shown in FIG. 6, the three-dimensional display device 1according to the embodiment may be incorporated within, for example, aportable phone 9.

Subsequently, how the three-dimensional display device 1 constructed asdescribed above and in accordance with the embodiment operates, i.e., amethod, constructed in accordance with the embodiments for displaying athree-dimensional image and a two-dimensional image will be explainedbelow. FIG. 8 shows an optical model illustrating how thethree-dimensional display device according to the embodiment operates.As shown in FIG. 8, when a light source 10 is turned on, light exitingthe light source 10 enters the display panel 2. At this point, a controldevice (not shown) drives the display panel 2, allowing an image forleft eye and an image for right eye to be displayed respectively by anaggregate of sub-pixels 41 for left eye and an aggregate of sub-pixels42 for right eye. Then, lights incident on the sub-pixel 41 for left eyeand the sub-pixel 42 for right eye in the display panel 2 transmitthrough those sub-pixels and propagate to the lenticular lens 3.Thereafter, those lights are refracted by the lenticular lens 3 and exitthe lenticular lens, and then, propagate to areas EL and ER,respectively. In this case, when an observer moves his/her eyes so thata left eye 61 is positioned in the area EL and a right eye 62 ispositioned in the area ER, an image for left eye (hereinafter, referredto also as a left eye image) is input to the left eye 61 and at the sametime, an image for right eye (hereinafter, referred to also as a righteye image) is input to the right eye 62. When a parallax exists betweenthe image for left eye and the image for right eye, the observer is ableto identify those images as a three-dimensional image. When no parallaxexists between those images, the observer is able to identify the imagesas a two-dimensional image.

In this case, light from the sub-pixel 41 for left eye passes throughone cylindrical lens 3 a corresponding to the sub-pixel 41 for left eyeand exits the lens 3 a, and then, propagates to the area EL.Accordingly, the left eye 61 positioned in the area EL does not identifythe pitch b of the sub-pixels 41 for left eye, but identifies a pitch Lof the cylindrical lenses 3 a as a width of an image to be displayed,which width corresponds to one pixel and is parallel to the horizontaldirection 12. Since the cylindrical lenses are disposed so as tocorrespond to the sub-pixel 41 for left eye and the sub-pixel 42 forright eye as described above, the array pitch L of the cylindricallenses is approximately twice the array pitch b of the sub-pixels. Thatis, the width of an image to be displayed on one display pixel, whichwidth is parallel to the horizontal direction 12, is identified as(2×b). Although the above-described explanation has been made of asub-pixel for left eye and a left eye, the explanation can similarly beapplied to a sub-pixel for right eye and a right eye because ofleft-right symmetric feature of the optical model shown in FIG. 8.

On the other hand, since the vertical direction 11 of an image to bedisplayed corresponds to the longitudinal direction of the cylindricallens 3 a, the effects of cylindrical lens cannot be produced.Accordingly, as is the case with a general two-dimensional displaydevice, a width of an image to be displayed, which width corresponds toone display pixel and is parallel to the vertical direction 11, equalsthe array pitch a of the sub-pixels for left eye or the sub-pixels forright eye in the vertical direction 11.

To make vertical and horizontal resolutions of an image to be displayedequal to each other, one display pixel making up an image to bedisplayed needs to be configured to make the width in the verticaldirection 11 and the width in the horizontal direction 12 equal to eachother. As described above, the width of display pixel in the verticaldirection is a and the width thereof in the horizontal direction is(2×b), and therefore, when those widths are made equal to each other,the vertical and horizontal resolutions of an image to be displayedbecome equal to each other. That is, the following expression 9 results.The following expression 10 results from the following expression 9.Those expressions exclusively mean that a ratio of the pitch of thesub-pixels arranged in the longitudinal direction (vertical direction11) of the lenticular lens to the pitch of the sub-pixels arranged inthe direction (horizontal direction 12) orthogonal to the longitudinaldirection of the lenticular lens is 2:1.a=2×b  (Expression 9)a:b=2:1  (Expression 10)

As described above, in the embodiment, one display pixel has providedtherein two sub-pixels, i.e., the sub-pixel 41 for left eye and thesub-pixel 42 for right eye, and therefore, the display device of theembodiment is able to display a three-dimensional image. Furthermore,since a ratio of the width a of each of the sub-pixels in the verticaldirection 11 to the width b of each of the sub-pixels in the horizontaldirection 12 is 2:1, the display pixel is caused to take a shape ofsquare. Accordingly, the shape of display pixel becomes a square at thetime of display of three-dimensional image. This allows an image to bedisplayed to have high visibility.

Moreover, beneficial effects produced by employment of the embodimentare enlarged especially when character information is displayed as athree-dimensional image. The reason for this is that when reduction inthe vertical or horizontal resolution of an image to be displayedoccurs, lack of a vertical or horizontal line making up the characterinformation occurs and an observer faces extreme difficulty inidentifying the character information. Accordingly, when the verticaland horizontal resolutions of an image to be displayed are made equal,the character information can particularly preferably be displayed in athree-dimensional form.

Furthermore, to allow the three-dimensional display device 1 accordingto the embodiment to display a two-dimensional image, the display devicemay be configured so that the same information is displayed by thesub-pixels for left eye and the sub-pixels for right eye. This allowsinformation to be identified by left and right eyes to become the sameand therefore parallax information, which exists in case of display ofthree-dimensional image, does not exist, permitting an image, which isto be displayed, to be identified as a two-dimensional image. In thiscase, the resolution of an image to be displayed is the same as thatachieved at the time of display of three-dimensional image and thedisplay pixel is caused to take a shape of square. As described above,in the embodiment, the resolutions achieved at the time of display ofthree-dimensional image and at the time of display of two-dimensionalimage can be made equal to each other, and therefore, even when thethree-dimensional image and the two-dimensional image are displayed in ablended fashion, an observer never feels uncomfortable, allowing athree-dimensional image to be displayed at any location where atwo-dimensional image is to be displayed. That is, an image is displayedon the screen of the three-dimensional display device so that when athree-dimensional image is displayed by the pixels, an image for lefteye and an image for right eye, both images having parallax information,are displayed by the sub-pixels for left eye and the sub-pixels forright eye, respectively and when a two-dimensional image is displayed bythe pixels, an image for left eye and an image for right eye, bothimages having the same information, i.e., no parallax information, aredisplayed by the sub-pixels for left eye and the sub-pixels for righteye, respectively, thereby allowing a three-dimensional image andtwo-dimensional image to be displayed in a blended fashion at anylocation where an image is to be displayed.

Still furthermore, since the three-dimensional image/two-dimensionalimage display device according to the embodiment employs a lenticularlens as means for displaying a three-dimensional image, it has anadvantage over the display device using a parallax barrier in that ablack fringe due to a parallax barrier is not produced and loss of lightis small.

The three-dimensional image/two-dimensional image display deviceaccording to the embodiment can preferably be applied to a portabledevice such as a cellular phone and is capable of displaying apreferable three-dimensional image and two-dimensional image. When thethree-dimensional image/two-dimensional image display device accordingto the embodiment is applied to a portable device, an observer is ableto optionally adjust positional relationship between his/her both eyesand a display screen, which operation is impossible to perform when thethree-dimensional image/two-dimensional image display device accordingto the embodiment is applied to a large scale display device, andtherefore, the observer is able to find a optimal visible range withoutdelay. Moreover, the three-dimensional image/two-dimensional imagedisplay device according to the embodiment can be applied not only to acellular phone but to a portable terminal device such as a portableterminal, PDA, game machine, digital camera, and digital video camera.

It should be appreciated that the focal distance of a lenticular lens ispreferably set to be different from a distance between the lenticularlens and the display pixel. This allows reduction in variations inbrightness of an image to be displayed, which variations are caused bythe light shield section partitioning the display pixels when anobserver changes his/her observing position, and further allowsbrightness of an image to be displayed to become uniform regardless ofobserver's observing positions.

To explain the above-described beneficial effects, how the size of eachpart of a dual eye type three-dimensional image display deviceincorporating therein a typical display panel and lenticular lens isdetermined will be first explained. FIG. 9 shows an optical modelillustrating a dual eye type three-dimensional image display deviceusing a typical lenticular lens. As shown in FIG. 9, the dual eye typethree-dimensional image display device is constructed such that a focaldistance of a lenticular lens 3 is equal to a distance between an apexof the lenticular lens 3 and pixels of a display panel 2. Theconfiguration of the three-dimensional display device other than theabove-described configuration is similar to that of thethree-dimensional display device 1 shown in FIG. 8 and constructed inaccordance with the embodiment.

In the device shown in FIG. 9, it is assumed that the distance betweenthe apex of the lenticular lens 3 and the pixels of the display panel 2is H, a refractive index and focal distance of the lenticular lens 3 isn and f, respectively, and a pitch of lenses making up the lenticularlens 3 is L. Display pixels of the display panel 2 are constructed suchthat a plurality of sets of one sub-pixel 41 for left eye and onesub-pixel 42 for right eye are arranged. Assume that a pitch of thosesub-pixels is P. Accordingly, an array pitch of the display pixels, eachconsisting of one sub-pixel 41 for left eye and one sub-pixel 42 forright eye, is 2P. One cylindrical lens 3 a is disposed so as tocorrespond to the display pixel consisting of the two sub-pixels, i.e.,one sub-pixel 41 for left eye and one sub-pixel 42 for right eye.

Additionally, assume that a distance between the lenticular lens 3 andan observer is an optimal observation distance OD, and a width overwhich one sub-pixel is projected in a magnified form on a plane apartfrom the lenticular lens 3 the distance OD, i.e., a width over whicheach of the sub-pixel 41 for left eye and the sub-pixel 42 for right eyeis projected in a magnified form on a virtual plane that is apart fromthe lens the distance OD and parallel to the lens is e. Furthermore,assume that a distance, in a horizontal direction 12, between the centerof the cylindrical lens 3 a located in the central portion of thelenticular lens 3 and the center of the cylindrical lens 3 a located inthe end portion of the lenticular lens 3 is W_(L), and a distance, inthe horizontal direction 12, between the center of the display pixelconsisting of the sub-pixel 41 for left eye and the sub-pixel 42 forright eye, both sub-pixels being located in the central portion of thedisplay panel 2, and the center of the display pixel that is located inthe end portion of the display panel 2 is W_(P). Still furthermore,assume that an incident angle of light to the cylindrical lens 3 a thatis located in the central portion of the lenticular lens 3 and an exitangle of light from the cylindrical lens 3 a is α and β, respectively,and an incident angle of light to the projection (cylindrical lens) 3 athat is located in the end portion of the lenticular lens 3 in thehorizontal direction 12 and an exit angle of light from the sameprojection 3 a is γ and δ. Still furthermore, assume that a differencebetween the distance W_(L) and the distance W_(P) is C, and the numberof the sub-pixels included in an area covering the distance W_(P) is 2m.

Since the array pitch L of the cylindrical lenses 3 a and the arraypitch P of the sub-pixels are related to each other, determination ofone of the two pitches allows determination of the other of the twopitches. However, in many cases, a lenticular lens is designed so as tofit a display panel and therefore the array pitch P of the sub-pixels ishandled as a constant. Moreover, selecting a material for the lenticularlens 3 allows determination of a refraction index n. In consideration ofthe refraction index determined as described above, the observationdistance OD between the lens and the observers and the width e overwhich one sub-pixel is projected in a magnified form on a plane apartfrom the lens the distance OD are determined to have a desired value.Through the use of those values, a distance H between the apex of thelens and the display pixel and the pitch L of the lenses are determined.Snell's law and a geometric relationship resulting from theabove-described assumption allow the following expressions 11 to 16 toresult. Moreover, the following expressions 17 to 19 result.n×sin α=sin β  (Expression 11)OD×tan β=e  (Expression 12)H×tan α=P  (Expression 13)n×sin γ=sin δ  (Expression 14)H×tan γ=C  (Expression 15)OD×tan δ=W _(L)  (Expression 16)W _(P) −W _(L) =C  (Expression 17)W _(P)=2×m×P  (Expression 18)W _(L) =m×L  (Expression 19)

The above-described expressions 11 to 13 allow the following expressions20 to 22 to result respectively.β=arctan (e/OD)  (Expression 20)α=arcsin ((1/n)×sin β)  (Expression 21)H=P/tan α  (Expression 22)

Additionally, the above-described expressions 16 to 19 allow thefollowing expression 23 to result. Moreover, the above-describedexpressions 18 and 19 allow the following expression 24 to result.Furthermore, the above-described expression 15 allows the followingexpression 25 to result.δ=arctan (mL/OD)  (Expression 23)C=2×m×P−m×L  (Expression 24)γ=arctan (C/H)  (Expression 25)

It should be noted that as described above, the distance B between theapex of the lenticular lens and the display pixel is usually made equalto the focal distance f of the lenticular lens, and therefore, thefollowing expression 26 results, and further, when assuming a curvatureradius of the lens is r, the curvature radius r is determined by thefollowing expression 27.f=H  (Expression 26)r=H×(n−1)/n  (Expression 27)

As shown in FIG. 9, it is assumed that an area that lights from all ofthe sub-pixels 42 for right eye reach is a right eye area 71 and an areathat lights from all of the sub-pixels 41 for left eye reach is a lefteye area 72. When an observer moves his/her eyes so that a right eye 62is positioned in the right eye area 71 and a left eye 61 is positionedin the left eye area 72, he/she is able to identify a three-dimensionalimage. Note that since binocular interval of the observer is constant,the observer is not necessarily able to move his/her eyes so that theright eye 62 and the left eye 61 are positioned at any location withinthe right eye area 71 and the left eye area 72, respectively, and theboth eyes are positioned in a specific area which allows the binocularinterval to be constant. That is, only when the midpoint between theright eye 62 and the left eye 61 is positioned within athree-dimensional visible range 7, the binocular vision is realized. Theposition at which a distance from the display panel 6 becomes theoptimal observation distance OD allows a length along the horizontaldirection 12 within the three-dimensional visible range 7 to becomemaximum and thereby permits the latitude to which displacement of theposition of observer in the horizontal direction 12 is allowed to becomemaximum. This means that the position at which the distance from thedisplay panel 6 becomes the optimal observation distance OD is a mostideal viewing position.

Furthermore, assume that a distance between a point that is locatedwithin the three-dimensional visible range 7 and farthest from thedisplay panel 6 and the display panel 6 is a maximum observationdistance D. To calculate the maximum observation distance D, as shown inFIG. 9, a distance between a point that is defined such that a light ray25 emitted from the left end of the sub-pixel 42 for right eye locatedin the right end portion of the display panel 2 is determined in thefigure and then a point apart from an optical system center line 26 thedistance equal to (e/2) in the left direction in the figure isdetermined on the light ray 25, and the display panel 2 may bedetermined. A geometric relationship shown in FIG. 9 allows thefollowing expression 28 to result, which in turn allows the maximumobservation distance D to be determined by the following expression 29.W _(L) :OD=(W _(L) +e/2):D  (Expression 28)D=OD×(W _(L) +e/2)/W _(L)  (Expression 29)

Based on the above-described geometric design, the three-dimensionalimage display device was simulated by a computer through the use ofcommercially available light ray tracing simulator. FIG. 10 shows anoptical model illustrating how the simulation is performed in theembodiment. As shown in FIGS. 5 and 6, in the present simulation, it isassumed that the display panel 2 has provided therein the sub-pixelswith a pitch P of 0.24 mm. Furthermore, to facilitate simulation, thedisplay panel 2 was assumed to have only one set of sub-pixel 41 forleft eye and sub-pixel 42 for right eye positioned in the centralportion of the display panel 2. Each of those sub-pixels is constructedsuch that a light-emitting area (not shown) is provided in the center ofthe sub-pixel and non light-emitting areas (not shown) are provided onboth sides of the light emitting area. The non light-emitting areascorrespond to a light shield section that is disposed for the purpose ofpreventing mixture of colors of images and sending a display signal to apixel. The width of one sub-pixel is 0.24 mm, which is equal to thearray pitch P of sub-pixels, and the width of the light-emitting area isassumed to be 0.186 mm. Accordingly, the width of one of the nonlight-emitting areas is 0.027 mm, which is determined by the expression(0.240-0.186)/2=0.027 mm.

Additionally, assume that the material making up the lenticular lens 3is polymethylmethacrylate (PMMA) having a refraction index n of 1.49 andthe observation distance OD between the lens and the observer is 280 mm.That is, a light reception surface 18 is disposed apart from the surfaceof the lenticular lens 3 a distance of 280 mm. Then, assume that thewidth e (refer to FIG. 9) over which one sub-pixel is projected in amagnified form on the light reception surface 18 is 65 mm and theaforementioned m has a value of 60. This leads to the conclusion thatbased on the above-described individual expressions, the distance Hbetween a lens surface and the display pixel is 1.57 mm, the focaldistance f of the lens is 1.57 mm, the pitch L of the lenses is 0.4782mm, and the curvature radius r of the lens is 0.5161 mm.

FIG. 11 is a graph resulting from the simulation, in which axis ofabscissas denotes the coordinate of a observing position on the lightreception surface and axis of ordinate denotes an illuminance at theobserving position. Note that the coordinate of viewing position isdetermined by reference to the optical system center line 26 shown inFIG. 9. As shown in FIG. 11, when the coordinate of observing positionis in the range of −60 mm to 0 mm, the illuminance becomes high and thevalue of the illuminance is uniform as a whole. That is, when the righteye is positioned in the range of −60 mm to 0 mm, a sufficient amount oflight enters the right eye. Furthermore, when the coordinate ofobserving position is in the range of 0 mm to +60 mm, the illuminancebecomes high and the value of the illuminance is uniform as a whole.That is, when the left eye is positioned in the range of 0 mm to +60 mm,a sufficient amount of light enters the left eye. This means that whenthe three-dimensional image display device is actually operated so thata left eye image is displayed by the sub-pixels for left eye and a righteye image is displayed by the sub-pixels for right eye, the left eyeimage is input to the left eye and the right eye image is input to theright eye, and in this case, separation of both images is sufficientlysecured, thereby allowing an observer to clearly identify thethree-dimensional image.

On the other hand, the illuminance around the observing positionscorresponding to the coordinates 0 mm and +60 mm is being reduced. Forthis reason, the observer at those observing positions cannot identifythe image. This is due to the influence of the light shield section. Inthe embodiment, especially at the time of display of three-dimensionalimage, the observer searches for observing positions to find a observingposition suited to view a three-dimensional image and potentially moveshis/her view point to the three-dimensional visible range. However, atthe time of display of two-dimensional image, the observer views thesame image through his/her left and right eyes and therefore theobserver cannot determine the location of the three-dimensional visiblerange. Accordingly, the probability with which the observer moveshis/her eyes to observing positions, at which the illuminance isreduced, to view a two-dimensional image becomes higher at the time ofdisplay of two-dimensional image than at the time of display ofthree-dimensional image, causing the observer to feel that the resultingquality of a two-dimensional image to be displayed is reduced.

In consideration of the above-described problems, the three-dimensionalimage/two-dimensional image display device according to the embodimentis configured so that the focal distance of the lenticular lens is madedifferent from the distance between the apex of the lenticular lens andthe display pixel. That is, instead of the aforementioned expression 26,the following expression 30 or expression 31 is used.f>H  (Expression 30)f<H  (Expression 31)Accordingly, light exiting the lenticular lens reaches the observer in aspread fashion. As a result, the influence of the light shield sectioncan be reduced. FIG. 12 is a graph resulting from the simulation, inwhich axis of abscissas denotes the coordinate of an observing positionon the light reception surface, axis of ordinate denotes an illuminanceat the observing position, and the focal distance of lenticular lens isassumed to be 1.88 mm. As shown in FIG. 12, it would be appreciated thatmaking the focal distance f of the lenticular lens different from thedistance H between the apex of the lenticular lens and the display pixelreduces the degree to which the illuminance at the observing positionscorresponding to the coordinates 0 mm and ±60 mm is reduced. This allowsthe observer not to view a two-dimensional image from an area in whichthe illuminance is reduced, thereby increasing the quality of atwo-dimensional image to be displayed.

The above-described beneficial effects can be obtained also when athree-dimensional image is displayed. However, at the time of display ofthree-dimensional image, the left eye image and the right eye image aredifferent from each other and therefore the probability of occurrence ofa cross talk, which is defined in this case such that the right eyeimage is viewed by the left eye, is increased. In contrast, at the timeof display of two-dimensional image, the left eye image and the righteye image are the same and therefore the cross talk never occurs.

It should be noted that although the focal distance is changed in theabove-described explanation, instead, the focal distance may be keptunchanged and the distance between the apex of the lenticular lens andthe display pixel may be changed in order to produce beneficial effectssimilar to the above-mentioned beneficial effects.

Furthermore, although the embodiment employs a transmissive liquidcrystal display panel as a display panel, the invention is not limitedto the embodiment, but may employ a reflective liquid crystal displaypanel or a semi-transmissive liquid crystal display panel having atransmissive region and a reflective region provided in each of pixels.Additionally, a method for driving a liquid crystal display panel wouldbe an active matrix method such as a TFT (Thin Film Transistor) methodand TFD (Thin Film Diode) method, or a passive matrix method such as anSTN (Super Twisted Nematic liquid crystal) method. Moreover, theinvention may employs as a display panel, other than the liquid crystaldisplay panel, for example, an organic electroluminescence displaypanel, plasma display panel, CRT (Cathode-Ray Tube) display panel, LED(Light Emitting Diode) display panel, field emission display panel, orPALC (Plasma Address Liquid Crystal) panel.

Furthermore, although the embodiment has been explained as an exampleapplied to the case where an image is viewed from two view points andaccordingly, one display pixel consists of two sub-pixels, the inventioncan similarly be applied to the case where an image is viewed from N (Nis an integer greater than 2) number of view points.

Still furthermore, although the embodiment employs a lenticular lens,the embodiment may employ a fly-eye lens instead of lenticular lens.Still furthermore, the embodiment may be configured to display a colorimage on a time-sharing method.

Second Embodiment

Subsequently, a second embodiment of the invention will be explainedbelow. FIG. 13 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 14 is a top viewillustrating a pitch of sub-pixels arranged in a display panel. As shownin FIGS. 9 and 10, the embodiment is different from the aforementionedfirst embodiment in that a display panel 2 has color display means suchas a color filter and as a result, one display pixel is comprised of sixprimary color sub-pixels that are viewed from two view points. Moreover,three cylindrical lenses 3 a of a lenticular lens 3 correspond to onedisplay pixel, a set of a red sub-pixel 411 for left eye and a greensub-pixel 422 for right eye corresponds to one cylindrical lens 3 a, aset of a blue sub-pixel 413 for left eye and a red sub-pixel 421 forright eye corresponds to another cylindrical lens 3 a, and a set of agreen sub-pixel 412 for left eye and a blue sub-pixel 423 for right eyecorresponds to still another cylindrical lens 3 a. That is, one displaypixel has the red sub-pixel 411 for left eye, green sub-pixel 422 forright eye, blue sub-pixel 413 for left eye, red sub-pixel 421 for righteye, green sub-pixel 412 for left eye, and blue sub-pixel 423 for righteye arranged one by one in a line in this order along a horizontaldirection 12. Furthermore, a pitch a of sub-pixels arranged in thelongitudinal direction (vertical direction 11) of the lenticular lens 3and a pitch b of the sub-pixels arranged in a direction (horizontaldirection) orthogonal to the longitudinal direction of the lenticularlens 3 satisfy the following expression 32.a:b=3×N:1  (Expression 32)

A three-dimensional display device according to the embodiment isconfigured so that an image to be displayed is viewed from two viewpoints, i.e., N in the expression 32 is 2, and therefore, a b=6:1results from the above-described expression 32. Moreover, as shown inFIG. 13, the six sub-pixels are arranged in a line along the short sidesof those sub-pixels to form one display pixel and therefore the displaypixel is caused to take a shape of square. The configuration andoperation of the embodiment other than the above-described configurationis similar to that of the first embodiment.

According to the embodiment, a color image can be displayed. Beneficialeffects of the embodiment other than the above-described beneficialeffects are similar to those of the aforementioned first embodiment.That is, a color three-dimensional image/two-dimensional image displaydevice can be achieved which is capable of displaying athree-dimensional image without reducing resolution, simultaneouslydisplaying a two-dimensional image and three-dimensional image with thesame resolution, and displaying a three-dimensional image andtwo-dimensional image in a blended fashion at any location where animage is to be displayed.

It should be noted that color arrangement employed in thethree-dimensional display device of the embodiment is only an exampleand the invention is in no way limited to the order observed in theabove color arrangement. Furthermore, although the three-dimensionaldisplay device allowing view from two view points has been shown in theembodiment, the invention is not limited to such configuration, but maybe applied to a display device allowing view from N (N is an integer notless than 3) number of view points.

Third Embodiment

Subsequently, a third embodiment of the invention will be explainedbelow. FIG. 15 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 16 is a top viewillustrating a pitch of sub-pixels arranged in the display device. Asshown in FIGS. 11 and 12, the embodiment is different from theaforementioned second embodiment in how the sub-pixels are arrangedwithin a display pixel. As a result, the embodiment is constructed suchthat one cylindrical lens 3 a of a lenticular lens 3 corresponds to onedisplay pixel and a direction in which the same-color areas, each beingcomprised of color display means such as a color filter, aresequentially arranged is orthogonal to the longitudinal direction of thelenticular lens, i.e., is a horizontal direction 12.

That is, a three-dimensional display device 1 of the embodiment has onedisplay pixel provided therein so that a red sub-pixel 411 for left eye,a green sub-pixel 412 for left eye and a blue sub-pixel 413 for left eyeare arranged in a line in this order along the vertical direction 11,and further, a red sub-pixel 421 for right eye, a green sub-pixel 422for right eye and a blue sub-pixel 423 for right eye are arranged in aline in this order along the vertical direction 11. Additionally, thered sub-pixel 411 for left eye and the red sub-pixel 421 for right eyeare arranged in a line along the horizontal direction 12, the greensub-pixel 412 for left eye and the green sub-pixel 422 for right eye arearranged in a line along the horizontal direction 12, and the bluesub-pixel 413 for left eye and the blue sub-pixel 423 for right eye arearranged in a line along the lateral direction 12. Furthermore, a pitcha of sub-pixels arranged in the longitudinal direction (verticaldirection 11) of the lenticular lens and a pitch b of the sub-pixelsarranged in a direction (horizontal direction 12) orthogonal to thelongitudinal direction of the lenticular lens satisfy the followingexpression 33.a:b=N:3  (Expression 33)

The three-dimensional display device according to the embodiment allowsview from two view points, i.e., corresponds to the case where N=2 andtherefore a:b=2:3 results from the above-described expression 33.Moreover, as shown in FIG. 15, the six sub-pixels are arranged in amatrix of two columns and three rows to form one display pixel andtherefore the display pixel is caused to take a shape of square. Theconfiguration and operation of the embodiment other than theabove-described configuration and operation are similar to those of thefirst embodiment.

According to the aforementioned second embodiment, one display pixel hasthe (3×N) number of sub-pixels arranged in a direction (horizontaldirection 12) orthogonal to the longitudinal direction of the lenticularlens. Whereas in the embodiment, three sub-pixels are arranged in thelongitudinal direction of the lenticular lens and N number of sub-pixelsare arranged in a direction orthogonal to the longitudinal direction,allowing the sub-pixels to be arranged in a distributed fashion in thevertical direction 11 and horizontal direction 12 within the displaypanel. As a result, the degree of how many sub-pixels are integrated inthe horizontal direction 12 within the display panel is reduced,advantageously facilitating manufacture of display device.

It should be noted that color arrangement employed in the embodiment isonly an example and the invention is in no way limited to the orderobserved in the above color arrangement. Furthermore, although thethree-dimensional display device allowing view from two view points hasbeen shown in the embodiment, the invention is not limited to suchconfiguration, but may be applied to a display device allowing view fromN (N is an integer not less than 3) number of view points.

Fourth Embodiment

Subsequently, a fourth embodiment of the invention will be explainedbelow. FIG. 17 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 18 is a top viewillustrating a pitch of sub-pixels arranged in the display device. Asshown in FIGS. 13 and 14, the embodiment is different from theaforementioned third embodiment in how primary color sub-pixels arearranged within a display pixel. Although the aforementioned thirdembodiment has, as shown in FIG. 16, the same color sub-pixels arrangedin a line in the horizontal direction 12, the embodiment has, asexemplarily shown in FIGS. 13 and 14, a red sub-pixel 411 for left eyeand a blue sub-pixel 423 for right eye are arranged in a line in thehorizontal direction 12, a green sub-pixel 412 for left eye and a redsub-pixel 421 for right eye are arranged in a line in the horizontaldirection 12, and a blue sub-pixel 413 for left eye and a greensub-pixel 422 for right eye are arranged in a line in the horizontaldirection 12. That is, the sub-pixels corresponding to the individualcolors are arranged in a mosaic pattern. Moreover, a positionalrelationship between the sub-pixels is the same relative to a centralaxis of a cylindrical lens 3 a of a lenticular lens 3 and threesub-pixels are arranged adjacent to one another to form a set of primarycolor sub-pixels with primary colors, red, blue and green.

The embodiment and the aforementioned third embodiment are differentfrom each other in that the primary color sub-pixels of the thirdembodiment are arranged in a stripe pattern and the primary colorsub-pixels of the embodiment are arranged in a mosaic pattern, allowingthe display device of the embodiment to be suited to display an image ofnatural scene, etc. The configuration, operation and beneficial effectsof the embodiment other than the above-described configuration,operation and beneficial effects are similar to those of theaforementioned third embodiment.

It should be noted that color arrangement employed in the embodiment isonly an example and the invention is in no way limited to the orderobserved in the above color arrangement. Furthermore, the invention isnot limited to the three-dimensional display device allowing view fromtwo view points, but may be applied to a display device allowing viewfrom N (N is an integer not less than 3) number of view points.

Fifth Embodiment

Subsequently, a fifth embodiment of the invention will be explainedbelow. FIG. 19 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 20 is a top viewillustrating a pitch of sub-pixels arranged in the display device. Theembodiment is different from the aforementioned first embodiment in thatin the embodiment, a pitch a of sub-pixels arranged in the longitudinaldirection (vertical direction 11) of lenticular lens and a pitch b ofthe sub-pixels arranged in a direction (horizontal direction 12)orthogonal to the longitudinal direction of lenticular lens do notsatisfy the aforementioned expression 10, but satisfy the followingexpression 34. Note that a pitch L of a lenticular lens and a pitch P ofsub-pixels take on the values determined by the aforementionedexpressions 11 to 19. The configuration and operation of the embodimentother than the above-described configuration and operation are similarto those of the aforementioned first embodiment.a:b=L:P  (Expression 34)

As shown in FIGS. 15 and 16, since an observer views the sub-pixelsthrough the lenticular lens 3, the length of sub-pixel in the horizontaldirection 12 appears magnified by the lenticular lens 3 to (L/P)×b. Onthe other hand, the apparent length of sub-pixel in the verticaldirection 11 is kept unchanged and equal to a. In the embodiment, thepitch of the sub-pixels arranged satisfies the aforementioned expression34 and therefore the apparent length a of sub-pixel in the longitudinaldirection 11 becomes equal to the apparent length (L/P)×b of sub-pixelin the horizontal direction 12. As a result, the display pixel isallowed to appear as a perfect square when the observer views a displaypanel 2 through the lenticular lens 3. This further improves thevisibility of an image to be displayed and improves especially andsignificantly the visibility of a character to be displayed. Beneficialeffects of the embodiment other than the above-described beneficialeffects are similar to those of the first embodiment.

Sixth Embodiment

Subsequently, a sixth embodiment of the invention will be explainedbelow. FIG. 21 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 22 is a top viewillustrating a pitch of sub-pixels arranged in the display device. Theembodiment is different from the aforementioned second embodiment inthat in the embodiment, a pitch a of the sub-pixels arranged in thelongitudinal direction (vertical direction 11) of lenticular lens and apitch b of the sub-pixels arranged in a direction (horizontal direction12) orthogonal to the longitudinal direction of lenticular lens do notsatisfy the aforementioned expression 32, but satisfy the followingexpression 35. The configuration of the embodiment other than theabove-described configuration is similar to that of the aforementionedsecond embodiment.a:b=3×L:P  (Expression 35)

As shown in FIGS. 17 and 18, since an observer views sub-pixels througha lenticular lens 3, the length of sub-pixel in the horizontal direction12 appears magnified by the lenticular lens 3 to (L/P)×b. Furthermore,since one display pixel has the sub-pixels of three colors arranged inthe horizontal direction 12, the apparent length of display pixel in thehorizontal direction 12 is equal to 3×(L/P)×b. On the other hand, theapparent length of sub-pixel in the vertical direction 11 is keptunchanged, i.e., is equal to a and since one display pixel has onesub-pixel disposed along the vertical direction 11, the apparent lengthof display pixel in the vertical direction 11 also is equal to a. In theembodiment, since the pitch of sub-pixels arranged satisfies theaforementioned expression 35, the apparent length a of display pixel inthe vertical direction 11 becomes equal to the apparent length 3×(L/P)×bof display pixel in the horizontal direction 12. As a result, whensub-pixels are arranged as shown in FIGS. 17, 18 and an observer viewsthe display panel 2 through the lenticular lens 3, the display pixel isallowed to appear as a perfect square. This further enhances thevisibility of an image to be displayed and in particular, significantlyenhances the visibility of a character to be displayed. Beneficialeffects of the embodiment other than the above-described beneficialeffects are similar to those of the aforementioned second embodiment.

Seventh Embodiment

Subsequently, a seventh embodiment of the invention will be explainedbelow. FIG. 23 is a perspective view illustrating an image displaydevice according to the embodiment and FIG. 24 is a top viewillustrating a pitch of sub-pixels arranged in the display device. Theembodiment is different from the aforementioned third embodiment in thatin the embodiment, a pitch a of sub-pixels arranged in the longitudinaldirection of lenticular lens and a pitch b of the sub-pixels arranged ina direction orthogonal to the longitudinal direction of lenticular lensdo not satisfy the above-described expression 33, but satisfy thefollowing expression 36. Note that a pitch L of cylindrical lenses oflenticular lens and a pixel-pitch P of sub-pixels take on the valuesdetermined by the aforementioned expression 11 to 19. The configurationand operation of the embodiment other than the above-describedconfiguration and operation are similar to those of the aforementionedthird embodiment.a:b=L/3:P  (Expression 36)

As shown in FIGS. 19 and 20, since an observer views sub-pixels througha lenticular lens 3, the length of sub-pixel in a horizontal direction12 appears magnified by the lenticular lens 3 to (L/P)×b. Furthermore,since one display pixel has two sub-pixel arranged in the horizontaldirection 12, the apparent length of display pixel in the horizontaldirection 12 also is equal to (L/P)×b. On the other hand, the apparentlength of sub-pixel in the vertical direction 11 is kept unchanged,i.e., is equal to a and since one display pixel has three sub-pixels ofthree colors' arranged in the vertical direction 11, the apparent lengthof display pixel in the vertical direction 11 is equal to 3×a. In theembodiment, since the pitch of the sub-pixels arranged satisfies theaforementioned expression 36, the apparent length 3×a of display pixelin the vertical direction 11 becomes equal to the apparent length(L/P)×b of display pixel in the horizontal direction 12. As a result,when sub-pixels are arranged as shown in FIGS. 19, 20 and an observerviews the display panel 2 through the lenticular lens 3, the displaypixel is allowed to appear as a perfect square. This further enhancesthe visibility of an image to be displayed and in particular,significantly enhances the visibility of a character to be displayed.Beneficial effects of the embodiment other than the above-describedbeneficial effects are similar to those of the aforementioned thirdembodiment.

It should be noted that as is the case with the aforementioned fourthembodiment, the embodiment may be configured so that the sub-pixelshaving the same color are arranged in a mosaic pattern in the displaypanel 2.

Eighth Embodiment

Subsequently, an eighth embodiment of the invention will be explainedbelow. FIG. 25 is a perspective view illustrating an image displaydevice according to the embodiment. Furthermore, a top view illustratinga pitch of sub-pixels arranged in the display device is the same as thatshown in FIG. 7. As shown in FIG. 25, the embodiment is different fromthe aforementioned first embodiment in that a parallax barrier 8 isprovided instead of lenticular lens. The configuration of the embodimentother than the above-described configuration is similar to that of theaforementioned first embodiment.

Then, how a three-dimensional display device of the embodiment operateswill be explained with reference to FIGS. 21 and 4. AS shown in FIG. 25,a light source (not shown) emits light and the light enters a displaypanel 2. At this point, in the display panel 2, a left eye image isdisplayed by the aggregation of sub-pixels 41 for left eye and a righteye image is displayed by the aggregation of sub-pixels 42 for righteye. Then, the lights incident on the sub-pixel 41 for left eye and thesub-pixel 42 for right eye, both sub-pixels being provided in thedisplay panel 2, transmit through those sub-pixels and propagate to theparallax barrier 8. Thereafter, those lights transmit through slits 8 aof the parallax barrier 8 and exit the slits, and then, propagate toareas EL and ER (refer to FIG. 8), respectively. In this case, when anobserver moves his/her eyes so that a left eye 61 is positioned in thearea EL and a right eye 62 is positioned in the area ER, the left eyeimage is input to the left eye 61 and at the same time, the right eyeimage is input to the right eye 62. When a parallax exists between theleft eye image and the right eye image, the observer is able to identifythose images as a three-dimensional image. When no parallax existsbetween those images, the observer is able to identify the images as atwo-dimensional image.

Since the embodiment employs the parallax barrier 8, the embodiment hasan advantage over an example employing a lenticular lens in that areduction in the quality of an image to be displayed, which reduction iscaused by the pattern in the lens, never occurs. Beneficial effects ofthe embodiment other than the above-described beneficial effects aresimilar to those of the aforementioned first embodiment. Note that theaforementioned second to seventh embodiments also are able to employ aparallax barrier instead of lenticular lens.

In the description of the aforementioned first to eighth embodiments, animage display device has been explained as a three-dimensionalimage/two-dimensional image display device allowing view from two viewpoints, i.e., a view point for left eye and a view point for right eye,and being capable of displaying both three-dimensional image andtwo-dimensional image. However, the image display device according tothe invention is not limited to the above-described configuration, butmay be an image display device allowing view from three or more viewpoints and/or allowing an observer to view through his/her both eyes animage from the individual view points. Therefore, when one image displaydevice displays images different from one another so that the images areviewed from view points different from one another and a plurality ofobservers view the image display device from angles different from oneanother, the plurality of observers are able to view the imagesdifferent from one another. Furthermore, when one image display devicedisplays images different from one another so that the images are viewedfrom view points different from one another and an observer changeshis/her viewing angle, the observer is able to view a plurality ofimages by switching between views of the plurality of images. In thefollowing description of a ninth embodiment of the invention, such animage display device is explained.

Ninth Embodiment

Subsequently, a ninth embodiment of the invention will be explainedbelow. FIG. 26 is a perspective view illustrating a portable terminaldevice according to the embodiment and FIG. 27 shows an optical modelillustrating how an image display device according to the embodimentoperates. As shown in FIG. 26, in the embodiment, an image displaydevice is incorporated within a cellular phone 9 as a portable terminaldevice. Furthermore, the embodiment is different from the aforementionedfirst embodiment in that a direction in which cylindrical lenses 3 amaking up a lenticular lens 3 are arranged is a vertical direction 11,i.e., the vertical direction of an image to be displayed and thevertical direction of the cylindrical lens 3 a is a horizontal direction12, i.e., the horizontal direction of an image to be displayed.Moreover, as shown in FIG. 27, a direction in which a sub-pixel 43 forfirst view point and a sub-pixel 44 for second view point are arrangedwithin one display pixel of a display panel 2 is the vertical direction11 in which the cylindrical lenses 3 a are arranged. Note that in FIG.26, to simplify illustration, only four cylindrical lenses 3 a areshown, however, actually, the cylindrical lenses 3 a are provided so asto correspond to the number of display pixels arranged in the verticaldirection 11. The configuration of the embodiment other than theabove-described configuration is similar to that of the aforementionedfirst embodiment.

Then, how the image display device of the embodiment operates will beexplained. As shown in FIG. 27, a light source 10 emits light and thelight enters the display panel 2. In this case, in the display panel 2,an image for first view point is displayed by the sub-pixels 43 forfirst view point and an image for second view point is displayed by thesub-pixels 44 for second view point. Then, the lights incident on thesub-pixel 43 for first view point and the sub-pixel 44 for second viewpoint, both sub-pixels being provided in the display panel 2, transmitthrough those sub-pixels and propagate to the lenticular lens 3.Thereafter, those lights are refracted by the cylindrical lens 3 a ofthe lenticular lens 3 and exit the cylindrical lens 3 a, and then,propagate to areas E1 and E2, respectively. The areas E1 and E2 arearranged along the vertical direction 11. In this case, when an observermoves his/her both eyes so that both eyes are positioned in the area E1,the observer is able to view the image for first view point and when theobserver moves his/her eyes so that both eyes are positioned in the areaE2, the observer is able to view the image for second view point.

In the embodiment, only changing the angle of the cellular phone 9allows the observer to position his/her both eyes in the area E1 or E2and thereby, advantageously permits the observer to view the image forfirst view point or the image for second view point. Particularly, whenthe image for first view point and the image for second view point areassociated with each other, the observer is able to view the individualimages simply by changing a viewing angle and therefore the cellularphone becomes highly convenient for a user. Note that when a pluralityof images to be viewed from a plurality of view points are arranged in adistributed fashion in the horizontal direction and an observer is in aposition from which the observer views images to be viewed fromdifferent view points through his/her left and right eyes, the observeris confused and cannot identify the images to be viewed from theindividual view points. In contrast, as shown in the description of theembodiment, when a plurality of images to be viewed from a plurality ofview points are arranged in a distributed fashion in the verticaldirection, an observer is able to view images to be viewed from theindividual view points through his/her both eyes without fail, allowingthe observer to easily identify those images. Beneficial effects of theembodiment other than the above-described beneficial effects are similarto those of the aforementioned first embodiment. Note that theconfiguration of the embodiment can be applied also to theaforementioned second to eighth embodiments.

1. An image display device comprising: a display panel which is to beviewed from N number of view points and includes a Plurality of displaypixels arranged in a matrix, each display pixel have M×N (M and N eachrepresent a natural number) number of sub-pixels, said M×N number ofsub-pixels included in each of said display pixels being formed within asquare area; and a lenticular lens for distributing light rays from saidsub-pixels individually to said view points, and wherein said displaypanel is monochrome display panel and M represents 1, and wherein whenassuming a pitch of said sub-pixels arranged in longitudinal directionalong a ridge projection of said lenticular lens is a and a pitch ofsaid sub-pixels arranged in a direction orthogonal to said longitudinaldirection of said lenticular lens is b, an expression a:b=N:1 results.2. An image display device comprising: a display panel which is to beviewed from N number of view points and includes a plurality of displaypixels arranged in a matrix, each display pixel having M×N (M and N eachrepresent a natural number) number of sub-pixels, said M×N number ofsub-pixels included in each of said display pixels being formed within asquare area; and a lenticular lens for distributing light rays from saidsub-pixels individually to said view points, and wherein said displaypanel is a color display panel comprising sub-pixels of three primarycolors and M represents 3, and wherein when assuming a pitch of saidsub-pixels arranged in a longitudinal direction along a ridge projectionof said lenticular lens is a and a pitch of said sub-pixels arranged ina direction orthogonal to said longitudinal direction of said lenticularlens is b, and expression a:b=3×N:1 results.
 3. An image display devicecomprising: a display panel which is to be viewed from N number of viewpoints and includes a plurality of display pixels arranged in a matrix,each display pixel having M×N (M and N each represent a natural number )number of sub-pixels, said M×N number of sub-pixels included in each ofsaid display pixels being formed within a square area; and a lenticularlens for distributing light rays from said sub-pixels individually tosaid view points, and wherein said display panel is a color displaypanel comprising sub-pixels of three primary colors and M represents 3,and wherein when assuming a pitch of said sub-pixels arranged in alongitudinal direction along a ridge projection of said lenticular lensis a and a pitch of said sub-pixels arranged in a direction orthogonalto said longitudinal direction of said lenticular lens is b, anexpression a:b=N:3 results.
 4. The image display device according toclaim 3, wherein said primary color sub-pixels having the same color arearranged in a direction orthogonal to said longitudinal direction ofsaid lenticular lens.
 5. The image display device according to claim 3,wherein said primary color sub-pixels having the same color are arrangedin a direction orthogonal to said longitudinal direction of saidlenticular lens.
 6. An image display device comprising: a display panelwhich is to be viewed from N number of view points and includes aplurality of display pixels, each including N (N represents a naturalnumber) number of sub-pixels; and a lenticular lens, said image displaydevice being further constructed such that when assuming a pitch of alens array in said lenticular lens is L, a pitch of said sub-pixels ofsaid display pixel is P, a pitch of said sub-pixels arranged in alongitudinal direction along a ridge projection of said lenticular lensis a, and a pitch of said sub-pixels arranged in a direction orthogonalto said longitudinal direction of said lenticular lens is b, saidpitches satisfy the following expression:a:b=L:P.
 7. The image display device according to claim 6, wherein saidprimary color sub-pixels having the same color are arranged in adirection orthogonal to said longitudinal direction of said lenticularlens.
 8. The image display device according to claim 6, wherein a set ofthree sub-pixels having the same relative positional relationship to acentral axis of said lenticular lens and positioned adjacent one anotherconstitutes primary color sub-pixels with primary colors, red, blue andgreen.
 9. The image display device according to claim 6, wherein a focaldistance of said lenticular lens and a distance between an apex of saidlens and said pixel are different from each other.
 10. The image displaydevice according to claim 6, wherein said longitudinal direction alongsaid ridge projection of said lenticular lens is a horizontal directionof an image to be displayed.
 11. The image display device according toclaim 6, wherein said display pixel is configured so that said displaypixel is to be viewed from two view points and comprises a sub-pixel forleft eye and a sub-pixel for right eye, wherein an image for left eyeand an image for right eye are displayed by sub-pixels for left eye andsub-pixels for right eye, respectively, and wherein at the time ofdisplay of three-dimensional image, images with parallax are displayedby said sub-pixels for left eye and said sub-pixels for right eye, andwherein at the time of display of two-dimensional image, the same imagesare displayed by said sub-pixels for left eye and said sub-pixels forright eye.
 12. The image display device according to claim 6, whereinsaid display panel is a liquid crystal display panel.
 13. A portableterminal device comprising said image display device described in claim6.
 14. The portable terminal device according to claim 13, wherein saidportable terminal device is a cellular phone, portable terminal, PDA,game machine, digital camera or digital video camera.
 15. An imagedisplay device comprising: a display panel which is to be viewed from Nnumber of view points and includes a plurality of display pixels, eachincluding 3×N (N represents a natural number) number of primary colorsub-pixels; and a lenticular lens, said image display device beingfurther constructed such that when assuming a pitch of a lens array insaid lenticular lens is L, a pitch of said sub-pixels of said displaypixel is P, a pitch of said sub-pixels arranged in a longitudinaldirection along a ridge projection of said lenticular lens is a, and apitch of said sub-pixels arranged in a direction orthogonal to saidlongitudinal direction of said lenticular lens is b, said pitchessatisfy the following expression:a:b=3×L:P.
 16. The image display device according to claim 15, wherein afocal distance of said lenticular lens and a distance between an apex ofsaid lens and said pixel are different from each other.
 17. The imagedisplay device according to claim 15, wherein said longitudinaldirection along said ridge projection of said lenticular lens is ahorizontal direction of an image to be displayed.
 18. The image displaydevice according to claim 15, wherein said display pixel is configuredso that said display pixel is to be viewed from two view points andcomprises a sub-pixel for left eye and a sub-pixel for right eye,wherein an image for left eye and an image for right eye are displayedby sub-pixels for left eye and sub-pixels for right eye, respectively,and wherein at the time of display of three-dimensional image, imageswith parallax are displayed by said sub-pixels for left eye and saidsub-pixels for right eye, and wherein at the time of display oftwo-dimensional image, the same images are displayed by said sub-pixelsfor left eye and said sub-pixels for right eye.
 19. The image displaydevice according to claim 15, wherein said display panel is a liquidcrystal display panel.
 20. A portable terminal device comprising saidimage display device described in claim
 15. 21. The portable terminaldevice according to claim 20, wherein said portable terminal device is acellular phone, portable terminal, PDA, game machine, digital camera ordigital video camera.
 22. An image display device comprising: a displaypanel which is to be viewed from N number of view points and includes aplurality of display pixels, each including 3×N (N represents a naturalnumber) number of primary color sub-pixels; and a lenticular lens, saidimage display device being further constructed such that when assuming apitch of a lens array in said lenticular lens is L, a pitch of saidsub-pixels of said display pixel is P, a pitch of sub-pixels arranged ina longitudinal direction along a ridge projection of said lenticularlens is a, and a pitch of said sub-pixels arranged in a directionorthogonal to said longitudinal direction of said lenticular lens is b,said pitches satisfy the following expression:a:b=L/3:P.
 23. The image display device according to claim 22, wherein afocal distance of said lenticular lens and a distance between an apex ofsaid lens and said pixel are different from each other.
 24. The imagedisplay device according to claim 22, wherein said longitudinaldirection along said ridge projection of said lenticular lens is ahorizontal direction of an image to be displayed.
 25. The image displaydevice according to claim 22, wherein said display pixel is configuredso that said display pixel is to be viewed from two view points andcomprises a sub-pixel for left eye and a sub-pixel for right eye,wherein an image for left eye and an image for right eye are displayedby sub-pixels for left eye and sub-pixels for right eye, respectively,and wherein at the time of display of three-dimensional image, imageswith parallax are displayed by said sub-pixels for left eye and saidsub-pixels for right eye, and wherein at the time of display oftwo-dimensional image, the same images are displayed by said sub-pixelsfor left eye and said sub-pixels for right eye.
 26. The image displaydevice according to claim 22, wherein said display panel is a liquidcrystal display panel.
 27. A portable terminal device comprising saidimage display device described in claim
 22. 28. The portable terminaldevice according to claim 27, wherein said portable terminal device is acellular phone, portable terminal, PDA, game machine, digital camera ordigital video camera.
 29. An image display device comprising: a displaypanel which is to be viewed from N number of view points and includes aplurality of display pixels arranged in a matrix, each display pixelhaving M×N (M and N each represent a natural number) number ofsub-pixels, said M×N number of sub-pixels included in each of saiddisplay pixels being formed within a square area; and a parallax barrierfor distributing light rays from said sub-pixels individually to saidview points, wherein said display panel is a monochrome display paneland M represents 1, and wherein when assuming a pitch of said sub-pixelsarranged in a longitudinal direction of a slit opening of said parallaxbarrier is a and a pitch of said sub-pixels arranged in a directionorthogonal to said longitudinal direction of said slit opening is b,said pitches satisfy the following expression:a:b=N:1.
 30. An image display device comprising: a display panel whichis to be viewed from N number of view points and includes a plurality ofdisplay pixels arranged in a matrix, each display pixel having M×N (Mand N each represent a natural number) number of sub-pixels, said M×Nnumber of sub-pixels included in each of said display pixels beingformed within a square area; and a parallax barrier for distributinglight rays from said sub-pixels individually to said view points,wherein said display panel is a color display panel comprisingsub-pixels of three primary colors and M represents 3, and wherein whenassuming a pitch of sub-pixels arranged in a longitudinal direction of aslit opening of said parallax barrier is a and a pitch of saidsub-pixels arranged in a direction orthogonal to said longitudinaldirection of said slit opening is b, said pitches satisfy the followingexpression:a:b=3×N:1.
 31. An image display device comprising: a display panel whichis to be viewed from N number of view points and includes a plurality ofdisplay pixels arranged in a matrix, each display pixel having M×N (Mand N each represent a natural number) number of sub-pixels, said M×Nnumber of sub-pixels included in each of said display pixels beingformed within a square area; and a parallax barrier for distributinglight rays from said sub-pixels individually to said view points whereinsaid display panel is a color display panel comprising sub-pixels ofthree primary colors and M represents 3, and wherein when assuming apitch of said sub-pixels arranged in a longitudinal direction of a slitopening of said parallax barrier is a and a pitch of said sub-pixelsarranged in a direction orthogonal to said longitudinal direction ofsaid slit opening is b, said pitches satisfy the following expression:a:b=N:3.
 32. The image display device according to claim 31, whereinprimary color sub-pixels having the same color are arranged in adirection orthogonal to said longitudinal direction of said slitopening.
 33. The image display device according to claim 31, wherein aset of three sub-pixels having the same relative positional relationshipto a center line of said slit opening and positioned adjacent oneanother constitutes primary color sub-pixels with primary colors, red,blue and green.
 34. The image display device according to claim 31,wherein said longitudinal direction of said slit opening of saidparallax barrier is a horizontal direction of an image to be displayed.35. An image display device comprising: a display panel which is to beviewed from N number of view points and includes a plurality of displaypixels arranged in a matrix, each display pixel having M×N (M and N eachrepresent a natural number) number of sub-pixels, said M×N number ofsub-pixels included in each of said display pixels being formed within asquare area; and a lenticular lens for distributing light rays from saidsub-pixels individually to said view points, and wherein said displaypixels configured so that said display pixel is to be viewed from twoview points and comprises a sub-pixel for left eye and a sub-pixel forright eye, wherein an image for left eye and an image for right eye aredisplayed by sub-pixels for left eye and sub-pixels for right eye,respectively, and wherein at the time of display of three-dimensionalimage, images with parallax are displayed by said sub-pixels for lefteye and said sub-pixels for right eye, and wherein at the time ofdisplay of two-dimensional image, the same images are displayed by saidsub-pixels for left eye and said sub-pixels for right eye.
 36. An imagedisplay device comprising: a display panel which is to be viewed from Nnumber of view points and includes a plurality of display pixelsarranged in a matrix, each display pixel having M×N (M and N eachrepresent a natural number) number of sub-pixels, said M×N number ofsub-pixels included in each of said display pixels being formed within asquare area; and a lenticular lens for distributing light rays from saidsub-pixels individually to said view points, and wherein a focaldistance of said lenticular lens and a distance between an apex of saidlens and said pixel are different from each other, and wherein saiddisplay pixel is configured so that said display pixel is to be viewedfrom two view points and comprises a sub-pixel for left eye and asub-pixel for right eye, wherein an image for left eye and an image forright eye are displayed by said sub-pixels for left eye and sub-pixelsfor right eye, respectively, and wherein at the time of display ofthree-dimensional image, images with parallax are displayed by saidsub-pixels for left eye and said sub-pixels for right eye, and whereinat the time of display of two-dimensional image, the same images aredisplayed by said sub-pixels for left eye and said sub-pixels for righteye.
 37. A display panel comprising a plurality of display pixelsarranged in a matrix, each display pixel being to be viewed from N viewpoints and including N (N represents a natural number) number ofsub-pixels, wherein said display panel is a monochrome display panel andwhen assuming a pitch of said sub-pixels arranged in one direction is aand a pitch of said sub-pixels arranged in a direction orthogonal tosaid one direction is b, an expression a:b=N:1 results.
 38. The displaypanel according to claim 37, wherein said display panel is a liquidcrystal display panel.
 39. A color display panel comprising a pluralityof display pixels arranged in a matrix, each display pixel being to beviewed from N view points and including 3×N (N represents a naturalnumber) number of three primary color sub-pixels, said display panelbeing further constructed such that when assuming a pitch of saidsub-pixels arranged in one direction is a and a pitch of said sub-pixelsarranged in a direction orthogonal to said one direction is b, anexpression a:b=3×N:1 results.
 40. The display panel according to claim39, wherein said display panel is a liquid crystal display panel.
 41. Acolor display panel comprising a plurality of display pixels arranged ina matrix, each display pixel being to be viewed from N view points andincluding 3×N (N represents a natural number) number of three primarycolor sub-pixels, said display panel being further constructed such thatwhen assuming a pitch of said sub-pixels arranged in one direction is aand a pitch of said sub-pixels arranged in a direction orthogonal tosaid one direction is b, an expression a:b=N:3 results.
 42. The displaypanel according to claim 41, wherein said display panel is a liquidcrystal display panel.
 43. An image display method, in which at the timeof display of three-dimensional image, at least M×2 number of sub-pixelsfor two view points of left-eye and right eye in M×N (M represents anatural number and N represents a natural number not less than 2) numberof sub-pixels for N view points included in each of a plurality ofdisplay pixels arranged in a matrix to constitute a display panel,display images with parallax and a lenticular lens distributes lightrays emitted from said sub-pixels for two view points individually tosaid view points; and at the time of display of two-dimensional image,said sub-pixels for two view points of left eye and right eye displayimages without parallax, said M×N number of sub-pixels included in eachof said display pixels being formed within a square area.
 44. An imagedisplay method, in which at the time of display of three-dimensionalimage, at least M×2 number of sub-pixels for two view points of left-eyeand right eye in M×N (M represents a natural number and N represents anatural number not less than 2) number of sub-pixels for N view pointsincluded in each of a plurality of display pixels arranged in a matrixto constitute a display panel, display images with parallax and aparallax barrier distributes light rays emitted from said sub-pixels fortwo view points individually to said view points; and at the time ofdisplay of two-dimensional image, said sub-pixels for two view points ofleft eye and right eye display images without parallax, said M×N numberof sub-pixels included in each of said display pixels being formedwithin a square area.